This non-provisional application claims priority based on Foreign United Kingdom Patent 00 27 305.2, Nov. 8, 2000.
1. Field of the Invention
This invention relates to subsea buoys.
2. Background and Prior Art
Subsea pipelines can be manoeuvred by securing buoyancy to them and moving them while they are underwater. In some case they are manoeuvred at great depth for example 1000 m or more. Once the pipeline is in the desired position the buoyancy can be released. It rises to the surface and may be recovered for re-use. The buoys are often large and ascend on release very rapidly. The path of the buoy is difficult to predict and the released buoys can present a major hazard to any surface ships or craft in the vicinity. The invention seeks to reduce this problem.
U.S. Pat. No. 4 096 818 describes a drogue type deceleration device which is actuated at a desired depth using a pressure control switch.
According to some embodiments of the invention there is provided subsea buoy for use in manoeuvring a submerged object, the buoy comprising
a) a buoyant body,
b) a first frangible link for securing the buoy to the object,
c) means for rupturing the first frangible link,
d) a drogue secured to the buoyant body by a second frangible link and by
e) means allowing the drogue to move on rupture of the second frangible link from a first configuration to a second configuration where the drogue is spaced apart from the buoyant body and
f) a third frangible link extending between the object and the drogue.